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A Forestry Field Trip Transecting the Sierra Nevada

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On this transect of the Sierra Nevadas we will be looking at vegetation and climate and how elevation affects vegetation. There are significant difference even with small changes in elevation. We'll start in a oak woodland, move into the mixed conifer forest and then into alpine forest to 9000'.

Elements that allows plants to grow at certain elevations include soil temperature, air temperature, forest diseases and adaptations to soil disturbances. There are five major species in mixed conifer forests ponderosa pine, sugar pine, incense-cedar, Douglas-fir and white fir.

Stop 1: Dry Creek Road

This is about 1200'-1300' elevation and is a oak woodland ecosystem dominated by oaks. Dominance is measured by size of the predominate species and not the amount. Oak woodland is rapidly disappearing because of human development. This ecosystem is characterized by long hot dry summers with temperatures up to 100° and rainfall of 15"-20" in a three month period. Plants must go a long time without water.

Color is an adaption also. Bluer vegetation reflects more energy so the tree doesn't need as much water. Waxy coatings help prevent water molecules from exiting the leaves. Reduced leaf size actually gives more surface area and provides self-shading for the plant.

We view a valley oak, the California white oak, Quercus lobata, a deciduous tree. There are three sub-groups of oaks: black, intermediate and white. This oak has no prickle on the ends of the leaves. The wood structure is unique. The cells have a wax, tylose, which gives this oak its waterproof quality. The acorns are sweeter because of less acid but the natives preferred black oaks as their acorns had more protein. This white oak is a important food source for deer though.

We find fungi on a fallen branch which decomposes it with a chemical. On a branch are many galls. These are created by a wasp female "stinging" the branch and depositing eggs. The eggs produce a plant growth hormone which forces the tree to build up cambrian tissue for the wasp hatchlings to eat. When the tiny wasp becomes an adult it exits the gall. Galls weaken the branches and often ice storms break them off.

Next is a California coffeeberry, used by very desperate settlers for coffee. It is a native of the valley and has reflective blue leaves.

On a branch is a shelf fungus known as turkey tail, the last of the decomposers. It has vegetative white threads going through the wood to decompose it.

Farther on is coyote brush, Baccarus pillularis, which grows everywhere in California. On the coast it is one foot tall but grows taller the farther inland. It has a waxy leaf with a shiny surface. The bottom half of the leaf is smooth and the top half has teeth. It is shade intolerant so it drops leaves on the inside branches.

The white-leaf manzanita, Arctostaphylos vasida, uses two techniques to survive here. The color is light green to reflect energy. Its leaves are not flat but vertical and pivot with the sun to keep their edges toward the sun thus minimizing surface area. To get its seeds distributed it coats the hard coating with a sugar. Animals eat the seeds and their stomach acids weaken the seed coat. When deposited it has a supply of fertilizer and water and has been transported away from the parent plant. Hard seed coats evolved in a fire environment. Seeds under the parent need the fire conditions to grow and replace their parent.

A thicket of himalaya berry is like blackberry. It has a compound leaf and spines along the leaflet, larger ones on the stems and big spines on the canes to deter it from being eaten by anything but birds. Birds have transported this plant across the U.S.

There is poison-oak under an oak tree. It is a member of the cashew family. The oak is a black oak, Q. kelloggii, noted by the bristle at the end of the leaf. These trees are endangered because of their use in furniture. Besides sexual reproduction, it can reproduce vegetatively with suckers.

This area is an ecotone, an zone where low elevation plants are growing at their top limit and high elevation plants are growing at their bottom limit. The gray trees we see are digger pines, Pinus sabiniana, and the darker ones are ponderosa pines, P. ponderosa. Ponderosa have three needles to a fascicle (group).

Buckbrush, Ceanothus cunetas, has many branches and stays small because it has been constantly grazed by deer. Eventually the energy stored up the roots will cause it to grow up out of the reach of deer.

The soil temperature here is 54° F and the air temperature is 50° F. We drive farther up I-80 and see less digger pines and more ponderosa pines. The density of vegetation is increasing also.

Stop 2: Secret Town Road

This is 2800' and the air temperature is 45.8° F. This is a new ecosystem, mixed conifers. Here it rains 30"-40" a year in 2 to 3 months. It is dominated by coniferous trees, such as ponderosa pines and douglas-firs, Pseudotsuga menziesii. One of the broad leaf trees here is black oaks. There are intermediate oaks here which really aren't oaks. Tanoak, Lithocarpus densiflorus, does produce acorns. Of all the oaks this produces the most protein for wildlife, up to 1100 pounds of seeds per year. Tanoak has two forms a brush and a tree form, which can coexist.

The ground here has been disturbed by the construction of Hwy 80. The hillside has been compacted and cleared off and the topsoil is gone. The site has been so degraded that the trees in this area have needles only at the tips of branches and are small, an indication of stress.

Knobcone pines, Pinus attenuata, is a fire climax species. The needles are feathery looking and the cones are attached to the main branches. They remain on the tree so we can see this tree has 10 years of cones on it. This tree needs full sun and with its closed cones and needs fire to release the seeds. This way it gets its seeds into the fire cleared forest first before it can get shaded out. Man's fire suppression is not allowing these trees to live a natural life.

We see a sugar pine, P. lambertiana, on the hill. It has long straight branches and long cones. It is disappearing because of disease. It is the largest tree of the region and is valuable for its straight-grained lumber. We see a tanoak with douglas-firs under it. The intolerance to shade is why clear cutting allows the trees to grow as quickly as possible. There is no relation between the size of a tree and its age.

A sugar pine with its top out and smaller ones around it have yellowish dwarf mistletoe on them. This is one of the things killing them. It is rare that trees are killed by one thing but by multiple things. The mistletoe is specific to them and insidiously takes them under their control by having the tree send food to the mistletoe.

Rust is also on these trees, spread by spores. The rust is so adaptable it has eluded attempts to breed resistant trees. All five needle pines are disappearing.

The ground temperature here is 48.2° F.

Stop 3: Blue Canyon

This is at 5200'-5400' elevation. A big fire came through this area in 1960 and the trees here are all about the same size. The pines came in first with the firs and incense-cedars, Calocedrus decurrens, coming in under them. This is called succession. This stand will eventually be a white pine forest unless there is more fire. The ground cover is called squaw carpet and is close to the ground around the pines and acts as a nurse crop for new pine seedlings. White firs are the most shade tolerant with incense-cedar next. We core a ponderosa pine and find it is about 35 years old. The soil temperature here is 52.2° F and the air is 42.5° F.

We drive through the Martis Valley which is in the rain shadow of the Sierras. In the distance the trees end as they go down into the valley. Here grows antelope brush and rabbit sage. There are dead trees on the hill. In the Tahoe basin about 30-40% of the trees are dead, mostly white fir. White fir took over from the pines because of the lack of fire. As white fir is not drought tolerant, California's recent drought years have taken their toll. There is lots of fuel here now for fires so a fire will be hot and possibly sterilize the soil.

As we drive up the road to Mt. Rose, we see higher elevation trees such as red fir. It has a white bark and the needles are close to the stem and turned upward. Also there are lodgepole pine, P. contorta, and mountain hemlock, Tsuga mertensiana.

Stop 4: Mt Rose

We are at 9000' and there is still 20' of snow on the ground. A five needle pine, Western white pine, P. monticola, has smaller cones than sugar pines although they are similarly elongated. The needles are shorter also. There is no sugar pine here. As you go higher in elevation one pine drops out of the ecosystem and another similar one takes its place. Beginning at 6000'-7000' is the subalpine ecosystem and the trees get smaller. Taller trees get ripped out by the winds.

A once tall lodgepole pine is nearby. It is a two needle pine and gets its name from the twist in the needles. This tree has been hit by lightning many times and has broken off. We see the twisting path of the lightning down the trunk. A side branch has turned upward to replace the missing top of the tree.

A five needle pine, whitebark pine, P. albicaulis, grows at elevations of 9000' and above. The cone is round with thick scales. It takes two years for them to mature. There are no pines above this one. It is important for Clark's nutcracker, a slate gray bird with white and black bands. It only eats the seeds of this tree. It holds the seeds between its feet and pecks them open. Seeds missed fall on the ground and this propagates the tree.

The mountain hemlock has needles in little groups. The tree can be recognized by the top of the tree being flopped over. The wood is brittle and of little lumber value. Its cones are small and purple.

Mike Price

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